Insert into boost::BIMAP using BOOST::associative property map … failed

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花落未央
花落未央 2021-01-20 03:37

With reference to my previously asked question about boost::bimaps and boost associative property maps interface here, I want to use Put and Get helper functions for my bim

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  • 2021-01-20 03:53

    In general you cannot update bimap entries via iterators:

    The relations stored in the Bimap will not be in most cases modifiable directly by iterators because both sides are used as keys of key-based sets. When a bimap left view iterator is dereferenced the return type is signature-compatible with a std::pair< const A, const B >.

    So there's your answer. Likewise, you couldn't

    my_bimap.left[2] = 19;
    

    http://www.boost.org/doc/libs/release/libs/bimap/doc/html/boost_bimap/the_tutorial/differences_with_standard_maps.html#boost_bimap.the_tutorial.differences_with_standard_maps.iterator__value_type

    Now, reading a bit more on there leads me to "suspect" the following solution:

    typedef bm::bimap< vertex_descriptor_t, bm::list_of<size_t> > vd_idx_bimap_t;
    

    Disclaimer: I don't know about the semantics that this changes (?) but it at least appears to support writable references. The below sample prints

    1 100
    value = 100
    1 100
    2 42
    

    See it Live On Coliru


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    #include <boost/bimap.hpp> 
    #include <boost/property_map/property_map.hpp> 
    #include <boost/bimap/property_map/set_support.hpp>
    #include <boost/bimap/list_of.hpp>
    #include <iostream> 
    
    using namespace boost; 
    
    int main() 
    {
        typedef int vertex_descriptor_t;
        namespace bm = boost::bimaps;
        typedef bm::bimap< vertex_descriptor_t, bm::list_of<size_t> > vd_idx_bimap_t;
        typedef boost::associative_property_map<vd_idx_bimap_t::left_map>   asso_vd_idx_bimap_t;
    
        // define bimap
        vd_idx_bimap_t        my_bimap;
        asso_vd_idx_bimap_t   my_asso_bimap(my_bimap.left);
    
        typedef typename vd_idx_bimap_t::value_type value_type;    
        my_bimap.insert( value_type( 1, 100 ) );
    
        // print bimap
        for(auto t = my_bimap.left.begin(); t != my_bimap.left.end(); ++t)
            std::cout << t->first << " " << t->second <<  "\n";
    
        int z = 1;
        std::cout << "value = " << get ( my_bimap.left, z ) << std::endl;    // prints correctly value = 100
    
        boost::put( my_asso_bimap, 2, 42 );
    
        for(auto t = my_bimap.left.begin(); t != my_bimap.left.end(); ++t)
            std::cout << t->first << " " << t->second <<  "\n";
     } 
    
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